I think most people would consider things like, working over 40 hours when you are salaried, routinely doing someone else’s job in addition to yours (like fixing their mistakes TOO much), skipping your lunch breaks to work.
Don’t get me wrong, doing those things SOMETIMES is ok. It’s when it becomes expected or ongoing that it’s a problem. Because no company is ever going to say “You are generating more profit for us at your own expense, slow down.”